A model of the tectonic stress state of Longmenshan Faults and adjacent area including direction and magnitude is derived from the spatial and temporal distribution of seismicity before and after Wenchuan Ms8.0 earthquake. This technique utilizes the assessment of spatial correlationship between stress change and seismicity change to obtain stress information. One detailed source models derived from the inversion of body wave, geology field survey and GPS data was used to calculate the stress change field from the Wenchuan mainshock, which was fit to the spatial distribution of seismicity. Agreement between the best-fitting background stress state from seismicity modeling and the background stress state inferred from focal mechanisms was found to be consistent, showing that the spatial distribution of seismicity contains information about the stress state. The best fitting background stress state has its greatest principal compressive stress plunging 11° to N295°W, a large effective coefficient of friction 0.76 for Longmenshan area, and 75MPa for the magnitude of greatest principal stress, which is far less than the overburden pressure estimated from the pressure intact rock endured in 15 km depth.


The massive Ms8.0 earthquake that struck China's Sichuan province on the 12th of May, 2008, killing about 90,000 people and injuring hundreds of thousands more, showing a devastating force on the lives and property for the populated area, western Sichuan basin in China. The mainshock ruptured the boundary between the Longmenshan mountains and the Sichuan basin with as much as 9mof slip and more than 300 km long at depth along, and demonstrated the complex strike-slip and thrust motion that characterizes the region [Wang 2008; Xu et al. 2008]. Focal mechanism solution and GPS survey has shown that Longmenshan mountain's Kinematics characteristics is that vertical uplift accompanied by N-E horizontal motion, presenting an image of complex fault movement.

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